ELECTRONIC CONTROL UNIT (ECU)
For diagnosing electronic control system malfunctions, refer to TESTS W/CODES article. For testing ground and power circuits of ECU, use the following procedures. If necessary, refer to ECU control schematics. (Scheme 259)or (Scheme 260).
GROUND CIRCUITS
- Using an ohmmeter, check for continuity to ground on ECU ground terminals. Refer to the «ECU GROUND CIRCUITS»(ref-24457-S20802156772001010500000) table. Also (Scheme 259)and (Scheme 260). Resistance should be zero ohms. If not, repair open ground circuit.
- Using a DVOM, touch negative lead of voltmeter to a good ground. (Scheme 259)or (Scheme 260). Touch positive lead of voltmeter to each ground terminal. See «ECU GROUND CIRCUITS»(ref-24457-S20802156772001010500000) table. With vehicle running, voltmeter reading should be less than.1 volt. If voltmeter reading is greater than.1 volt, check for open, corrosion or loose connection on ground lead.
| Application | ECU Terminals |
|---|---|
| 2.5L | No. 1, 2 & 10 |
ECU GROUND CIRCUITS
Scheme 259
Scheme 260
- Using a voltmeter, check for battery voltage between ECU terminal No. 4 and ground. (Scheme 259)and (Scheme 260). If battery voltage is not present, check for an open in Red wire between ECU and battery.
- Turn ignition switch to the ON position. Using a voltmeter, check for battery voltage between ECU terminal No. 3 and ground. (Scheme 259)and (Scheme 260). If battery voltage is not present, check for an open in Black wire between ignition switch and terminal No. 3 of ECU, or check for a defective ignition switch.
- Connect a voltmeter between ground and ECU terminal No. 29. (Scheme 259)and (Scheme 260). Turn ignition switch to the START position. Battery voltage should be present between control unit terminal No. 29 and ground ONLY when ignition switch is in the START position. If voltage is not present, check for an open in Green wire between ECU terminal No. 29 and start relay, or check for a defective ignition switch.
OXYGEN (O2) SENSOR HEATING ELEMENT
Note. For additional oxygen sensor information, see TITANIA OXYGEN SENSOR TESTING article.
FUEL DELIVERY
Note. For fuel system pressure testing, see F BASIC TESTING article.
SYNC PULSE (STATOR)
Note. For this test, an analog voltmeter is needed. DO NOT remove distributor connector from distributor. Insert voltmeter leads into the backside of the distributor connector to make contact with terminals. Ensure that the connector is not damaged when inserting the tester probes.
EVAPORATIVE FUEL SYSTEM
To test fuel evaporation system, refer to TESTS W/CODES article.